1710 CXLVIIl. NAIADES. IPotamogeton, 



5. P. perfoliatus (perfoliate), Linn. ; Kimth, Emm. iii. 133 ; Renth. J'L 

 Austr. vii. 172. Leaves all submerged, alternate except under the peduncles and 

 branches where they are opposite, all sessile, ovate or almost orbicular, clasping- 

 the stem with broad rounded auricles which are sometimes united on the opposite 

 side, thin and many-nerved, f to l^in. long and often quite as broad. Stipules 

 only on very young shoots. Peduncles longer than the leaves. Spike cylindrical^ 

 rarely above 6 to 8 lines long. Nutlets scarcely beaked.— R. Br. Prod. 343 ; 

 F. v. M. Fragm. viii. 219 ; Eeichb. Ic. Fl. Germ. t. 29. 



Hab.: Southern \raters. 



6. P. crispus (crisped), Linn. ; Kunth, Emm. iii. 133 ; Benth. Fl. Aiistr.. 

 vii. 172. Leaves all submerged, alternate and contracted at the base, except 

 when under the branches or peduncles where th€y are opposite and stem- 

 clasping, all linear or narrow-oblong,, very obtuse, the margins usually undulate- 

 crisped, 1 to 2 or rarely nearly Sin. long, with a strong central nerve and a, 

 slender one on each side at some distance from it. Stipules only seen on th& 

 young shoots. Peduncles rather long. Spikes usually 4 to 5 lines long. Fruits, 

 rather large, distinctly beaked, the dorsal rib or ribs entire or rarely denticulate.. 

 — E. Br. Prod. 848 ; F. v. M. Fragm. viii. 217 ; Eeichb. Ic. Fl. Germ. t. 29. 



Hab.: Eoekhanipton, O'Shanesy; and many southern waters. 



Common in the northern hemifphere. The t.vpical form has ths leaves very much broadeu 

 thad in P. ohtnsifolius and much crisped on the edges, but the narrow-leaved forms come very 

 near to that species. 



7. P. obtusifolius (leaves obtuse). Men. et Koch ; Kunth, Enum. iii. 135 \. 

 Benth. Fl. Austr. vii. 172. Stems slender, terete, or somewhat flattened. Leaves- 

 all submerged, alternate, except under the peduncles or branches where they are 

 opposite, narrow-linear, entire, usually 3-nerved with a very few transverse veins^. 

 obtuse or almost acute, sessile and rounded or shortly contracted at the base^ 

 mostly IJ to Sin. long. Stipules often persistent and at length splitting into~ 

 threads. Peduncles not long. Spikes usually ^in. or rather longer, not very 

 dense. Nutlets about 1 J line long, with a straight or hooked beak, often, 

 rugose, the dorsal rib and lateral angles usually obtuse and scarcely diatinot 

 but sometimes more prominent and toothed. Seed usually much curved with 

 the upper end obliquely reflexed. — F. v. M. Fragm. viii. 216; Eeichb. Ic. Fl.. 

 Germ? t. 25,; P. gmviineus, E. Br. Prod. 343 ; Hook. f. Fl. Tasm. ii. 42 and of 

 some others. 



Hab.: Common in the southern waters. 



The P. ohtitiifolhis is one of the most generally spread over the area of the genus. 



8. P. pectinatus (comb-like), TJnn.; Kunth, Emm. iii. 137 ; Benth. Fl.. 

 Austr. vii. 173. Stems very slender, repeatedly dichotomous. Leaves all sub- 

 merged, very narrow-linear, 2 to Sin. long, 1-nerved most of them dilated at the 

 base into a rather long sheath, which is scarious at the edge and often projecting' 

 at the top into 2 small scarious lobes, the sheathing stipules of the other species 

 wanting or rarely sheathing the base of the peduncle. Peduncles usually bearing 

 several clusters of 2 or 3 flowers at some distance from each other, forming a 

 slender interrupted spike, rarely reduced to a single terminal cluster. Nutlets of 

 P. obtusifolius or rather smaller.^ — Eeichb. Ic. Fl. Germ. t. 19 ; P. marinus, Linn.;: 

 F. V. M. Fragm. viii. 217 ; Eeichb. Ic. Fl. Germ. t. 18. 



I' Hab.: Still waters, Jimbour, C. J. Gwyther. 



Very generally distributed over the area of the genus, in fvesh and brackish waters. 



4. RUPPIA, Linn. 



(After Henry Barnard Euppius.) 



Flowers hermaphrodite, in a. spike enclosed when young in the sheathing bases 

 of the floral leaves. Perianth none. Anthers 2, each with 2 distinct cells- 



